Aliphatic and aromatic amines are well known curing agents and are discussed in detail in many technical publications, e.g., "Epoxy Resins" by Lee and Neville (1957). Typical aromatic amines, used as epoxy curing agents, are metaphenylene diamine, methylene dianiline and diaminodiphenyl sulfone. Such amines are solid compounds which must be heated when mixed with polyepoxide resins. Curing temperatures and curing times are relatively high and long, but can be reduced somewhat with an accelerator, e.g., phenolic compound, aliphatic amine, imidazoles, or boron trifluoride amine complex.
Typical aliphatic amines used with the polyepoxide resins are diethylenetriamine, triethylenetetraamine and dicyandiamide. The former two react readily with epoxy resins at room temperature and, therefore, do not offer long pot lives to the formulation. Dicyandiamide is a high melting solid amine with low solubility in many solvents.
U.S. Pat. No. 4,366,108 describes curable compositions made from a liquid epoxy resin, a hindered aromatic amine, namely diethyltoluenediamine, and a curing accelerator. Typical accelerators are 1-methylimidazole, phenols, salicylic acid and boronfluoroamine complexes, such as BF3-acetoacetanilide, BF3-aniline complexes or BF3-monoethylamine.
A recent publication, Wiggins, "Curing Acceleration of a Hindered Aromatic Diamine-Epoxy System", 41st Annual Conference, Reinforced Plastics/Composites Institute, The Society of Plastics Industry, Inc., Jan. 27-31, 1986, Session 5-A, also discusses the use of various accelerators with hindered aromatic amines as curing compositions for epoxide systems. While some of the accelerators provided satisfactory gel times in these systems, Tg and/or shelf stability suffered from such materials.
The invention relates, therefore, to a liquid matrix system, based on a mixture of epoxide resin and an amine curing agent for the epoxide resin, for producing fibre-reinforced plastics components.